Pristinamycin is a streptogramin antibiotic produced by Streptomyces pristinaespiralis,which contains two chemically unrelated compounds,pristinamycin Ⅰ(PⅠ) and pristinamycin Ⅱ(PⅡ).The semi-synthetic derivatives of PⅠ and PⅡ have been approved in human medicine against a broad range of drug-resistant pathogens.Here,we report a combinatorial metabolic engineering strategy to improve PⅡ biosynthesis.